The present invention relates to enclosures for mounting electronic equipment and in particular to a uniquely designed housing having a plurality of compartments for mounting dimmer modules which supply electric power to lighting equipment such as incandescent lamps.
The enclosure according to the present invention is frequently referred to as a dimmer rack. Dimming control systems utilizing dimmer racks are already in use in many lighting control applications such as in architectural, theatrical and television settings. Such racks provide the mechanical and electrical means for mounting and electrically connecting a plurality of individual dimmer modules to input power and control signals. Each dimmer module is then used to control the electric power supplied to a specific group or bank of lighting devices such as incandescent lamps. The dimmer module responds to the input and power control signals transmitted to the dimmer modules through the circuitry of the dimmer rack and delivers measured amounts of electrical power through the electrical circuitry of the dimmer rack to the lighting devices to be operated.
In various embodiments of prior art dimmer racks, aluminum shell and chassis systems have been provided which accept predetermined numbers of plug-in dimmer modules from 6 to in excess of 200 and one or more plug-in control modules. Input and output connectors are located on the rear panel of such shell and chassis systems to which the input and control signals are connected and from which output power is delivered to the lighting fixtures to be operated.
Such prior art dimmer racks have certain problems associated with their design and use including the provision of removable shelving and partitions to provide the means for mounting the individual dimmer modules in the dimmer rack. To install or change the wiring connections to the dimmer modules, the user had to perform the attachment and removal of certain mechanical components before the wiring could be accomplished and the rack could be put into service. In many cases, the layout and mechanical design of the rack made this a difficult, inconvenient, and time-consuming task to do.
The physical location of various electrical interconnection points of prior art dimmer racks was also haphazard. Although the input, output and control signal distribution points were usually given due consideration as to positioning and location, the location of the electrically neutral connection point was frequently an afterthought, resulting in its being placed in difficult and inaccessible locations, making for intricate and difficult wiring problems.
Because of the significant power requirements entailed in dimming control systems, it is normal to use three-phase power in supplying electrical power to the lighting load. Prior art dimming systems have typically utilized a rack design wherein the groups of dimmer modules connected to different phases of input power are positioned in a side-by-side configuration. When the lighting load to be driven by the dimming system was extensive and entailed the use of a number of dimmer racks placed side by side, the rack-to-rack electrical bussing was a significant problem. In order to connect one rack to the next, it was necessary to find a suitable location for placing the bus bars. Typically they had to be placed at the rear of or in the base of the dimmer rack. The various phases then were cabled to the bus bars and in some cases cables were also utilized to complete the rack-to-rack electrical communications making the process both difficult and expensive.
Problems in isolating the phases from each other were also encountered.
Dimmer racks, according to the prior art, were also characterized by limited current interrupting capacity. In typical prior art systems, dimmer racks had an upper rating of 10,000 amps. In instances where a higher rating was required, additional fusing in the form of amp traps was provided. Prior art racks were typified by designs wherein the amp traps were mounted in inconvenient and hard-to-service locations.
In dimmer rack design, it has been recognized that provision for a back-up mode of operation for the dimmer control system is desirable. Such a mode of operation entailed the provision of some form of circuitry that would cause certain dimmer modules to receive power and keep certain lighting turned on, even in the event of a failure of the control console or control module electronics. Typically, this was done by providing a limited number of diodes which were hard wired into certain selected dimmer module circuits. The disadvantage of such a design is that it lacked flexibility, only a very specific, very limited number of circuits could be bypassed. There was no ability to pick and choose whether each and every module could be bypassed or not at the option of the user. Hard wiring of the diodes meant that they were usually either inaccessible or difficult to modify or rearrange.